In this sequel to the La Brassiere, Lena (Gigi Leung), Johnny (Lau Ching-wan) and Wayne (Louis Koo) are tasked with developing the "Mighty B" line of baby products. Since the last successful development of the "Mighty Bra", Johnny is now head of the department, he hires a neurotic secretary Sabrina (Rosamund Kwan). Lena and Wayne are planning their wedding, however, Wayne has "Baby-Phobia" which throws a wrench into their task of developing the premier "Mighty B" line of baby products. Lena hires child behavior expert Boey (Cecilia Cheung), to work with Wayne to overcome his phobia but things start to go awry when Wayne starts developing feelings for Boey.